The mental and underlying neural (neuro-cognitive) operations involved in the comprehension of words are fundamental to language based communication. Understanding how the brain identifies individual words from around fifty thousand or so possibilities in less than half a second, has been a continuing challenge for theorists in psychology, neuroscience and education. Finding the answer to this and related questions would represent a major step forward in basic language science, but also would provide a framework for helping isolate the neuro-cognitive locus of deficits in certain developmental language disorders. The overall goal of the proposed research is to continue our study of word comprehension processes from a neuro-cognitive perspective. The experiments outlined in this proposal are focused on providing answers to questions about the temporal dynamics (ERPs) and now the spatial organization (MEG and fMRI) of the neural networks that underlie the comprehension of words. The proposed research has four specific aims. In Aim 1 we propose to test a series of predictions about the temporal dynamics of visual word comprehension derived from our recently elaborated Bi-modal Interactive Activation Model (BIAM) of word processing. Experiments are proposed that use our well understood ERP masked priming paradigm, as well as two new novel experimental techniques. We will also extend the scope of our research in three new directions. In Aim 2 we propose a novel series of ERP studies designed to expand our study of comprehension to the auditory modality using our newly developed dichotic priming task. These studies will allow us to better elaborate the auditory side of the BIAM. In Aim 3 we propose experiments that test predictions from the BIAM at the interface between visual and spoken word processing, a level we hypothesize is critical to the process of learning to read. Finally, in Aim 4 we propose to augment our work on the temporal dynamics of word comprehension by using multi-modal imaging techniques. This will provide much needed information about the spatial organization of the neural networks involved in word comprehension and will allow us to add an anatomical component to our BIAM of word comprehension. Our long term goal is to extend these studies to normal children as well as those with word processing deficits including dyslexia and SLI. PUBLIC HEALTH RELEVANCE: Language use is the quintessential human cognitive ability, and fundamental to this ability is the skilled use of its elemental units, words. The primary goal of the research outlined in this application is to inform theories of both normal and abnormal word processing by providing insights into the neuro-cognitive underpinnings of word processing in young adults. This research will provide the basis for future studies aimed at providing a better understanding of the learning-to-read process in both normal and language impaired children.